Methods for forming a semiconductor device structure and related semiconductor device structures

ABSTRACT

Methods for forming a semiconductor device structure are provided. The methods may include forming a molybdenum nitride film on a substrate by atomic layer deposition by contacting the substrate with a first vapor phase reactant comprising a molybdenum halide precursor, contacting the substrate with a second vapor phase reactant comprise a nitrogen precursor, and contacting the substrate with a third vapor phase reactant comprising a reducing precursor. The methods provided may also include forming a gate electrode structure comprising the molybdenum nitride film, the gate electrode structure having an effective work function greater than approximately 5.0 eV. Semiconductor device structures including molybdenum nitride films are also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of, and claims priority to, U.S.patent application Ser. No. 16/924,595 filed Jul. 9, 2020 titled METHODSFOR FORMING A SEMICONDUCTOR DEVICE STRUCTURE AND RELATED SEMICONDUCTORDEVICE STRUCTURES, which is a continuation of, and claims priority to,U.S. patent application Ser. No. 16/038,024 filed Jul. 17, 2018 (nowU.S. Pat. No. 10,734,497) titled METHODS FOR FORMING A SEMICONDUCTORDEVICE STRUCTURE AND RELATED SEMICONDUCTOR DEVICE STRUCTURES, whichclaims the benefit of U.S. Provisional Patent Application Ser. No.62/534,085 filed Jul. 18, 2017, titled METHODS FOR FORMING ASEMICONDUCTOR DEVICE STRUCTURE AND RELATED SEMICONDUCTOR DEVICESTRUCTURES, the disclosures of which are hereby incorporated byreference in their entirety.

BACKGROUND Field of the Invention

The present disclosure relates generally to methods for forming asemiconductor device structure including a molybdenum nitride film andrelated semiconductor device structures.

Description of the Related Art

Metal-oxide-semiconductor (MOS) technology has conventionally utilizedn-type doped polysilicon as the gate electrode material. However, dopedpolysilicon may not be an ideal gate electrode material for advancednode applications. For example, although doped polysilicon isconductive, there may still be a surface region which can be depleted ofcarriers under bias conditions. This region may appear as an extra gateinsulator thickness, commonly referred to as gate depletion, and maycontribute to the equivalent oxide thickness. While the gate depletionregion may be thin, on the order of a few angstroms (Å), it may becomesignificant as the gate oxide thicknesses are reduced in advance nodeapplications. As a further example, polysilicon does not exhibit anideal effective work function (eWF) for both NMOS and PMOS devices. Toovercome the non-ideal effective work function of doped polysilicon, athreshold voltage adjustment implantation may be utilized. However, asdevice geometries reduce in advanced node applications, the thresholdvoltage adjustment implantation processes may become increasinglycomplex and impractical.

To overcome the problems associated with doped polysilicon gateelectrodes, the non-ideal doped polysilicon gate material may bereplaced with an alternative material, such as, for example, atransition metal nitride. For example, the properties of a transitionmetal nitride may be modified to provide a gate electrode structure witha more ideal effective work function for both the NMOS and PMOS devices,where the effective work function of the gate electrode, e.g., theenergy needed to extract an electron, must be compatible with thebarrier height of the semiconductor material. For example, in the caseof PMOS devices, the required effective work function is approximately5.0 eV.

Methods and semiconductor device structures are therefore desirable thatare able to provide a gate electrode structure including a transitionmetal nitride with appropriate physical and electrical properties.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form. These concepts are described in further detail in thedetailed description of example embodiments of the disclosure below.This summary is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is it intended to be used tolimit the scope of the claimed subject matter.

In some embodiments, methods for forming a forming a semiconductordevice structure are provided. The methods may comprise: forming amolybdenum nitride film on a substrate by atomic layer deposition,wherein forming the molybdenum nitride film comprises; contacting thesubstrate with a first vapor phase reactant comprising a molybdenumhalide precursor; contacting the substrate with a second vapor phasereactant comprising a nitrogen precursor selected from the groupcomprising ammonia (NH₃), hydrazine (N₂H₄), triazane (N₃H₅),tertbutylhydrazine (C₄H₉N₂H₃), methylhydrazine (CH₃NHNH₂), anddimethylhydrazine ((CH₃)₂N₂H₂); and contacting the substrate with athird vapor phase reactant comprising a reducing precursor selected fromthe group comprising hydrogen gas (H₂), silane (SiH₄), disilane (Si₂H₆),trisilane (Si₃H₈), tetrasilane (Si₄H₈), and acetylene (C₂H₂); andforming a gate electrode structure comprising the molybdenum nitridefilm, the gate electrode structure having an effective work functiongreater than approximately 5.0 eV.

In some embodiments semiconductor device structures are provided. Thesemiconductor device structures may comprise a PMOS transistor gatestructure, the PMOS transistor gate structure comprising a molybdenumnitride film and a gate dielectric disposed between the molybdenumnitride film and a semiconductor body, wherein the PMOS gate structurehas an effective work function greater than 5.0 eV.

For the purpose of summarizing the invention and advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught or suggested herein withoutnecessarily achieving other objects or advantaged as may be taught orsuggested herein.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments will becomereadily apparent to those skilled in the art from the following detaileddescription of certain embodiments having reference to the attachedfigures, the invention not being limited to any particular embodiment(s)disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming what are regarded as embodiments of theinvention, the advantages of embodiments of the disclosure may be morereadily ascertained from the description of certain examples ofembodiments of the disclosure when read in conjunction with theaccompanying drawings, in which:

FIG. 1 is simplified cross section view of a semiconductor devicestructure formed according to the embodiments of the disclosure;

FIG. 2 illustrates a reaction system configured to perform certainembodiments of the disclosure.

DETAILED DESCRIPTION

The illustrations presented herein are not meant to be actual view ofany particular material, structure, or device, but are merely idealizedrepresentations that are used to describe embodiments of the disclosure.

As used herein, the term “atomic layer deposition” (ALD) may refer to avapor deposition process in which deposition cycles, preferably aplurality of consecutive deposition cycles, are conducted in a processchamber. Typically, during each cycle, the precursor is chemisorbed to adeposition surface (e.g., a substrate surface or a previously depositedunderlying surface such as material from a previous ALD cycle), forminga monolayer or sub-monolayer that does not readily react with additionalprecursor (i.e., a self-limiting reaction). Thereafter, if necessary, areactant (e.g., another precursor or reaction gas) may subsequently beintroduced into the process chamber for use in converting thechemisorbed precursor to the desired material on the deposition surface.Typically, this reactant is capable of further reaction with theprecursor. Further, purging steps may also be utilized during each cycleto remove excess precursor from the process chamber and/or remove excessreactant and/or reaction byproducts from the process chamber afterconversion of the chemisorbed precursor. Further, the term “atomic layerdeposition,” as used herein, is also meant to include processesdesignated by related terms such as, “chemical vapor atomic layerdeposition”, “atomic layer epitaxy” (ALE), molecular beam epitaxy (MBE),gas source MBE, or organometallic MBE, and chemical beam epitaxy whenperformed with alternating pulses of precursor composition(s), reactivegas, and purge (e.g., inert carrier) gas.

As used herein, the term “substrate” may refer to any underlyingmaterial or materials that may be used, or upon which a device, acircuit or a film may be formed.

A subscript “x” for the molybdenum nitride film (e.g., MoN_(x)) may beused to designate that the molybdenum nitride is not necessarilystoichiometric, having a wide range of phases, with varyingmolybdenum/nitrogen ratios.

The present disclosure includes methods for forming semiconductor devicestructures and the semiconductor device structures themselves thatinclude a molybdenum nitride film formed by an atomic layer depositionprocess. The methods of the disclosure may include utilizing themolybdenum nitride film as a component of a gate electrode structurethereby forming a gate electrode structure with an effective workfunction more suitable for PMOS device structures. The disclosure mayalso include methods for forming gate electrode structures comprisingthin film molybdenum nitride films with increased effective workfunction in addition to reduced electrical resistivity. For example, theeffective work function of a gate electrode structure may vary as afunction of its thickness, i.e., the effective work function of the gateelectrode structure may decrease or increase with decreasing thicknessof the materials comprising the gate electrode. As device geometriesdecrease in advanced node applications, the thickness of thecorresponding device films, for example, such as the gate electrode, mayalso decrease with a corresponding change in the effective work functionof the film. Such a change in the effective work function of the gateelectrode at reduced thickness may result in a non-ideal effective workfunction for PMOS device structures. Methods and semiconductor devicestructures are therefore required to provide a more desirable molybdenumnitride film. Examples of such methods and semiconductor devicesstructures are disclosed in further detail below.

ALD is based on typically self-limiting reactions, whereby sequentialand alternating pulses of reactants are used to deposit about one atomic(or molecular) monolayer of material per deposition cycle. Thedeposition conditions and precursors are typically selected to provideself-saturating reactions, such that an adsorbed layer of one reactantleaves a surface termination that is non-reactive with the gas phasereactants of the same reactant. The substrate is subsequently contactedwith a different reactant that reacts with the previous termination toenable continued deposition. Thus, each cycle of alternated pulsestypically leaves no more than about one monolayer of the desiredmaterial. However, as mentioned above, the skilled artisan willrecognize that in one or more ALD cycles more than one monolayer ofmaterial may be deposited, for example if some gas phase reactions occurdespite the alternating nature of the process.

In an ALD-type process for depositing molybdenum nitride films(MoN_(x)), one deposition cycle may comprise exposing the substrate to afirst reactant, removing any unreacted first reactant and reactionbyproducts from the reaction space and exposing the substrate to asecond reactant, followed by a second removal step. The first reactantmay comprise a molybdenum precursor and the second reactant may comprisea nitrogen precursor.

Precursors may be separated by inert gases, such as argon (Ar) ornitrogen (N₂), to prevent gas-phase reactions between reactants andenable self-saturating surface reactions. In some embodiments, however,the substrate may be moved to separately contact a first vapor phasereactant and a second vapor phase reactant. Because the reactionsself-saturate, strict temperature control of the substrates and precisedosage control of the precursors is not usually required. However, thesubstrate temperature is preferably such that an incident gas speciesdoes not condense into monolayers nor decompose on the surface. Surpluschemicals and reaction byproducts, if any, are removed from thesubstrate surface, such as by purging the reaction space or by movingthe substrate, before the substrate is contacted with the next reactivechemical. Undesired gaseous molecules can be effectively expelled from areaction space with the help of an inert purging gas. A vacuum pump maybe used to assist in the purging.

According to some embodiments, ALD processes are used to form molybdenumnitride films on a substrate, such as an integrated circuit workpiece.In some embodiments of the disclosure each ALD cycle comprises twodistinct deposition steps or phases. In a first phase of the depositioncycle (“the molybdenum phase”), the substrate surface on whichdeposition is desired is contacted with a first vapor phase reactantcomprising a molybdenum precursor which chemisorbs onto the substratesurface, forming no more than about one monolayer of reactant species onthe surface of the substrate.

In some embodiments, the molybdenum precursor, also referred to hereinas the “molybdenum compound,” may comprise a molybdenum halide and theadsorbed monolayer may be terminated with halogen ligands. Themolybdenum precursor may therefore comprise a molybdenum chloride whichmay further comprise at least one of molybdenum trichloride (MoCl₃),molybdenum tetrachloride (MoCl₄), molybdenum pentachloride (MoCl₅), ormolybdenum hexachloride (MoCl₆). The molybdenum precursor may alsocomprise a molybdenum fluoride, such as, for example, molybdenumhexafluoride (MoF₆). The molybdenum precursor may further comprise amolybdenum carbonyl, such as, for example, molybdenum hexacarbonyl(Mo(CO)₆). In some embodiments of the disclosure, the molybdenumprecursor may comprise an organic molybdenum precursor, such as, forexample, tetrachloro(cyclopentadienyl)molybdenum. In some embodiments,the molybdenum precursor may comprise at least one halide ligand (e.g.,chloride or fluoride), or at least one metal-organic ligand, or at leastone organometallic ligand, or may even comprise a cyclic ligand (e.g.,cyclopentadienyl). In some embodiments, exposing the substrate to themolybdenum precursor may comprise pulsing the molybdenum precursor(e.g., the molybdenum pentachloride) over the substrate for a timeperiod of less than 20 seconds, or a time period less than 15 seconds,or a time period of less than 10 seconds, or even for a time period ofless than 5 seconds. In addition, during the pulsing of the molybdenumprecursor over the substrate the flow rate of the molybdenum precursormay be less than 1000 sccm, or less than 500 sccm, or less than 300sccm, or even less than 100 sccm.

Excess molybdenum source material and reaction byproducts (if any) maybe removed from the substrate surface, e.g., by purging with an inertgas. Excess molybdenum source material and any reaction byproducts maybe removed with the aid of a vacuum generated by a pumping system.

In a second phase of the deposition cycle (“the nitrogen phase”), thesubstrate is contacted with a second reactant comprising a nitrogenprecursor. In some embodiments of the disclosure, the nitrogen precursormay comprise a nitrogen based plasma (e.g., a plasma comprising nitrogenradicals, ions and atoms) and the nitrogen based plasma may be generatedby a remote plasma or alternatively by direct plasma. In someembodiments of the disclosure, methods may further comprising selectingthe nitrogen precursor to comprise at least one of ammonia (NH₃),hydrazine (N₂H₄), triazane (N₃H₅), tertbutylhydrazine (C₄H₉N₂H₃),methylhydrazine (CH₃NHNH₂), and dimethylhydrazine ((CH₃)₂N₂H₂).

In some embodiments, exposing the substrate to the nitrogen precursormay comprise pulsing the nitrogen precursor (e.g., ammonia) over thesubstrate for a time period of less than 20 seconds, or a time period ofless than 15 seconds, or a time period of less than 10 seconds, or evenfor a time period of less than 5 seconds. During the pulsing of thenitrogen precursor over the substrate the flow rate of the nitrogenprecursor may be less than 1000 sccm, or less than 500 sccm, or lessthan 300 sccm, or even less than 100 sccm.

The second vapor phase reactant comprising a nitrogen precursor mayreact with the molybdenum-containing molecules left on the substratesurface. Preferably, in the second phase nitrogen is incorporated intothe film by the interaction of the second vapor phase reactant with themonolayer left by the molybdenum source material. In some embodiments,reaction between the second vapor phase reactant comprising a nitrogenprecursor and the chemisorbed molybdenum metal species produces amolybdenum nitride thin film (MoN_(x)) over the substrate.

Excess second source chemical and reaction byproducts, if any, areremoved from the substrate surface, for example by a purging gas pulseand/or vacuum generated by a pumping system. Purging gas is preferablyany inert gas, such as, without limitation, argon (Ar), nitrogen (N₂) orhelium (He). A phase is generally considered to immediately followanother phase if a purge (i.e., purging gas pulse) or other reactantremoval step intervenes.

The deposition cycle in which the substrate is alternatively contactedwith the first vapor phase reactant (i.e., the molybdenum precursor) andthe second vapor phase reactant (i.e., the nitrogen precursor) may berepeated one or more times until a desired thickness of molybdenumnitride (MoN_(x)) is deposited. It should be appreciated that in someembodiments of the disclosure the order of the contacting of thesubstrate with the first vapor phase reactant and the second vapor phasereactant may be such that the substrate is first contacted with thesecond vapor phase reactant followed by the first vapor phase reactant.In addition in some embodiments the ALD process may comprise contactingthe substrate with the first vapor phase reactant one or more timesprior to contacting the substrate with the second vapor phase reactantone or more times and similarly may alternatively comprise contactingthe substrate with the second vapor phase reactant one or more timesprior to contacting the substrate with the first vapor phase reactantone or more times.

In some embodiments of the disclosure the ALD process for depositingmolybdenum nitride films (MoN_(x)) may comprise an additional thirdphase. For example, in some embodiments one deposition cycle maycomprise exposing the substrate to a first reactant, removing anyunreacted first reactant and reaction byproducts from the reactionspace, exposing the substrate to a second reactant, followed by a secondremoval step and exposing the substrate to a third reactant, followed bya third removal step. The first reactant may comprise a molybdenumprecursor and the second reactant may comprise a nitrogen precursor aspreviously described herein. In some embodiments, a third phase may beutilized in the ALD-process for depositing molybdenum nitride films(MoN_(x)) and the third phase may comprise a reducing precursor.

In a third phase of the deposition cycle (“the reducing phase”), thesubstrate is contacted with a third vapor phase reactant comprising areducing precursor. In some embodiments of the disclosure, methods mayfurther comprise selecting the reducing precursor to comprise at leastone of hydrogen (H₂), silane (SiH₄), disilane (Si₂H₆), trisilane(Si₃H₈), tetrasilane (Si₄H₁₀) or higher order silanes with the generalempirical formula Si_(x)H_((2x+2)). In general the reducing precursormay comprise a precursor which comprises a reducing agent, such as, forexample, acetylene (C₂H₂). In some embodiments of the disclosure, thereducing precursor may comprise a hydrogen (H₂) based plasma which maycomprise atomic hydrogen, hydrogen radicals, hydrogen plasma andhydrogen ions. For example, the hydrogen (H₂) based plasma may begenerated utilizing a direct plasma or alternatively a remote plasma. Inalternative embodiments of the disclosure, the reducing precursor maynot comprise a hydrogen plasma, hydrogen radicals, atomic hydrogen orhydrogen ions. For example, the reducing precursor may not be generatedby a direct plasma, a remote plasma, hot-wire or alternative means fordissociation molecular hydrogen.

In some embodiments, exposing the substrate to the reducing precursormay comprise pulsing the reducing precursor over the substrate for atime period of less than 60 seconds, or a time period of less than 30seconds, or a time period of less than 10 seconds, or a time period ofless than 5 seconds, or even for a time period of less than 1 second.During the pulsing of the reducing precursor over the substrate, theflow rate of the reducing precursor may be less than 1000 sccm, or lessthan 500 sccm, or less than 300 sccm, or even less than 100 sccm.

The third vapor phase reactant comprising a reducing precursor may reactwith the molybdenum nitride film left on the substrate surface.Preferably, in the third phase the third vapor phase reactant,comprising a reducing precursor, interacts with the molybdenum nitridefilm (MoN_(x)). In some embodiments, the interaction between the thirdvapor phase reactant comprising a reducing precursor and the molybdenumnitride film reduces the electrical resistivity of the molybdenumnitride film. For example, in some embodiments of the disclosure,utilizing a third vapor phase reactant comprising a reducing precursorthe methods may comprise forming a molybdenum nitride film to have anelectrical resistivity of less than 3000 μΩ-cm, or less than 2000 μΩ-cm,or less than 1200 μΩ-cm, or less than 800 μΩ-cm, or less than 600 μΩ-cm,or less than 400 μΩ-cm, or even less than 200 μΩ-cm.

Excess third source chemical and reaction byproducts, if any, areremoved from the substrate surface, for example by a purging gas pulseand/or vacuum generated by a pumping system. Purging gas is preferablyany inert gas, such as, without limitation, argon (Ar), nitrogen (N₂) orhelium (He). A phase is generally considered to immediately followanother phase if a purge (i.e., purging gas pulse) or other reactantremoval step intervenes.

In the example embodiments described herein the ALD deposition cycle maycomprise a sequence of contacting the substrate with a first vapor phasereactant, followed by a first purging cycle, contacting the substratewith a second vapor phase reactant, followed by a second purging cycleand contacting the substrate with a third vapor phase reactant followedby a third purging cycle. In alternative embodiments of the disclosurethe ALD deposition cycle may be performed by alternate sequencing of thefirst, second and third vapor phase reactants with the substrate, withintervening purging cycles. In addition, the ALD deposition cycle maycomprise one or more repetitions of each contacting step prior to asubsequent purging cycle.

In some embodiments of the disclosure the third phase of the depositioncycle, comprising the contacting of the substrate with a third vaporphase reactant comprising a reducing precursor may be performedconcurrently with the first phase and/or with the second phase of thedeposition cycle. For example, forming the molybdenum nitride film onthe substrate by ALD may comprise contacting the substrate with amolybdenum precursor whilst optionally also contacting the substratewith a reducing precursor, such that the molybdenum precursor and thereducing precursor simultaneously contact the substrate. In addition, insome embodiments, forming the molybdenum nitride film on the substrateby ALD may comprise contacting the substrate with a nitrogen precursorwhilst optionally also contacting the substrate with a reducingprecursor, such that the nitrogen precursor and the reducing precursorsimultaneously contact the substrate.

The ALD processes described herein, utilizing a molybdenum precursor anda nitrogen precursor (with an optional reducing precursor) to form amolybdenum nitride (MoN_(x)), may be performed in an ALD depositionsystem with a heated substrate. For example, in some embodiments,methods may comprise heating the substrate to temperature of greaterthan 400° C., or heating the substrate to a temperature of greater than450° C., or heating the substrate to a temperature of greater than 500°C., or even heating the substrate to a temperature of greater than 550°C.

The deposition rate of the molybdenum nitride film by ALD, which istypically presented as A/pulsing cycle, depends on a number of factorsincluding, for example, on the number of available reactive surfacesites or active sites on the surface and bulkiness of the chemisorbingmolecules. In some embodiments, the deposition rate of such molybdenumnitride films may range from about 0.1 to about 5.0 Å/pulsing cycle. Insome embodiments, the deposition rate can be about 0.1, 0.2, 0.3, 0.5,1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 Å/pulsing cycle.

The molybdenum nitride formed by the embodiments of the disclosure maytake the form MoN_(x) wherein x may range from approximately 0.75 toapproximately 1.8, or wherein x may range from approximately 0.8 toapproximately 1.5, or wherein x may range from 0.9 to approximately 1.3,or alternatively wherein x may range from approximately 0.95 toapproximately 1.2. The elemental composition ranges for MoN_(x) maycomprise Mo from about 30 atomic % to about 60 atomic %, or from about35 atomic % to about 55 atomic %, or even from about 40 atomic % toabout 50 atomic %. Alternatively the elemental composition ranges forMoN_(x) may comprise N from about 25 atomic % to about 65 atomic %, or Nfrom about 30 atomic % to about 60 atomic %, or even N from about 35atomic % to about 55 atomic %. In additional embodiments the MoN_(x) maycomprise less than about 20 atomic % oxygen, less than about 10 atomic %oxygen, less than about 5 atomic % oxygen, or even less than about 2atomic % oxygen. In further embodiments, the MoN_(x) may comprise lessthan about 10 atomic % hydrogen, or less than about 5 atomic % ofhydrogen, or less than about 2 atomic % of hydrogen, or even less thanabout 1 atomic % of hydrogen. In some embodiments, the MoN_(x) maycomprise Halide/Cl less than about 10 atomic %, or Halide/Cl less thanabout 5 atomic %, Halide/Cl less than about 1 atomic %, or evenHalide/Cl less than about 0.5 atomic %. In yet further embodiments, theMoN_(x) may comprise less than about 10 atomic % carbon, or less thanabout 5 atomic % carbon, or less than about 2 atomic % carbon, or lessthan about 1 atomic % of carbon, or even less than about 0.5 atomic %carbon. In the embodiments outlined herein, the atomic concentration ofan element may be determined utilizing Rutherford backscattering (RB S).

In some embodiments of the invention the molybdenum nitride films formedby the atomic layer deposition processes of the disclosure may have acubic crystallographic structure, whereas in alternative embodiments themolybdenum nitride films formed by the methods of the disclosure mayhave a tetragonal crystallographic structure.

In some embodiments of the disclosure, forming the molybdenum nitridefilm may comprise forming the molybdenum nitride film to a thickness ofless than 100 Angstroms, or to a thickness of less than 50 Angstroms, orto a thickness of less than 30 Angstroms.

The molybdenum nitride films formed by the ALD processes disclosedherein can be utilized in a variety of contexts, such as in theformation of gate electrode structures. One of skill in the art willrecognize that the processes described herein are applicable to manycontexts, including fabrication of PMOS transistors including planardevices as well as multiple gate transistors, such as FinFETs.

As a non-limiting example, and with reference to FIG. 1 , asemiconductor device structure 100 may comprise a transistor structureand may include a source region 102, a drain region 104, a channelregion 106 there between. A transistor gate structure 108 may comprise agate electrode 110 which may be separated from the channel region 106 bya gate dielectric 112. According to the teaching of the presentdisclosure, the gate electrode 110 may comprise a molybdenum nitridefilm formed by an atomic layer deposition process as described herein.As shown in FIG. 1 , in some embodiments the transistor gate structure108 may further comprise one or more additional conductive layers 114formed on the gate electrode 110. The one or more additional conductivelayers 114 may comprise at least one of polysilicon, a refractory metal,a transition metal carbide and a transition metal nitride.

In some embodiments, the semiconductor device structure 100 may comprisea PMOS transistor, the PMOS transistor may further comprise thetransistor gate structure 108. The PMOS transistor gate structure 108may comprise a gate electrode 110 comprising a molybdenum nitride filmand a gate dielectric 112 disposed between the molybdenum nitride filmand a semiconductor body 116.

As a non-limiting example embodiment the semiconductor device structure100 may comprise a silicon (Si) semiconductor body 116, a hafnium oxide(HfO₂) gate dielectric 112, a molybdenum nitride (MoN_(x)) gateelectrode 110 and an additional conductive layer 114 comprising titaniumnitride (TiN).

In some embodiments of the disclosure, forming a semiconductor devicestructure, such as semiconductor device structure 100, may compriseforming a gate electrode structure comprising a molybdenum nitride film,the gate electrode structure having an effective work function greaterthan approximately 4.9 eV, or greater than approximately 5.0 eV, orgreater than approximately 5.1 eV, or greater than approximately 5.2 eV,or greater than approximately 5.3 eV, or even greater than approximately5.4 eV. In some embodiments, the effective work function values givenabove may be demonstrated for an electrode structure comprising amolybdenum nitride film with a thickness of less than approximately 100Angstroms, or less than approximately 50 Angstroms, or less thanapproximately 40 Angstroms, or even less than approximately 30Angstroms. It should be noted that the embodiments of the disclosureallow for the formation of gate electrode structures comprising thinmolybdenum nitride films with increased effective work function, forexample, in some embodiments methods may comprise forming a gateelectrode structure comprising a molybdenum nitride film with athickness of less than 100 Angstroms with an effective work function ofgreater than approximately 5.0 eV. In further embodiments, methods maycomprise forming the gate electrode structure comprising a molybdenumnitride film with a thickness of less than 100 Angstroms with aneffective work function of greater than approximately 5.4 eV. In yetfurther embodiments, methods may comprise forming the gate electrodestructure comprising a molybdenum nitride film with a thickness of lessthan 30 Angstroms with an effective work function of greater thanapproximately 5.0 eV.

Embodiments of the disclosure may also include a reaction systemconfigured for forming the molybdenum nitride films of the presentdisclosure. In more detail, FIG. 2 schematically illustrates a reactionsystem 200 including a reaction chamber 202 that further includesmechanism for retaining a substrate (not shown) under predeterminedpressure, temperature, and ambient conditions, and for selectivelyexposing the substrate to various gases. A precursor reactant source 204may be coupled by conduits or other appropriate means 204A to thereaction chamber 202, and may further couple to a manifold, valvecontrol system, mass flow control system, or mechanism to control agaseous precursor originating from the precursor reactant source 204. Aprecursor (not shown) supplied by the precursor reactant source 204, thereactant (not shown), may be liquid or solid under room temperature andstandard atmospheric pressure conditions. Such a precursor may bevaporized within a reactant source vacuum vessel, which may bemaintained at or above a vaporizing temperature within a precursorsource chamber. In such embodiments, the vaporized precursor may betransported with a carrier gas (e.g., an inactive or inert gas) and thenfed into the reaction chamber 202 through conduit 204A. In otherembodiments, the precursor may be a vapor under standard conditions. Insuch embodiments, the precursor does not need to be vaporized and maynot require a carrier gas. For example, in one embodiment the precursormay be stored in a gas cylinder. The reaction system 200 may alsoinclude additional precursor reactant sources, such precursor reactantsource 206 which may also be couple to the reaction chamber by conduits206A as described above.

A purge gas source 208 may also be coupled to the reaction chamber 202via conduits 208A, and selectively supplies various inert or noble gasesto the reaction chamber 202 to assist with the removal of precursor gasor waste gasses from the reaction chamber. The various inert or noblegasses that may be supplied may originate from a solid, liquid or storedgaseous form.

The reaction system 200 of FIG. 2 , may also comprise a system operationand control mechanism 210 that provides electronic circuitry andmechanical components to selectively operate valves, manifolds, pumpsand other equipment included in the reaction system 200. Such circuitryand components operate to introduce precursors, purge gasses from therespective precursor sources 204, 206 and purge gas source 208. Thesystem operation and control mechanism 210 also controls timing of gaspulse sequences, temperature of the substrate and reaction chamber, andpressure of the reaction chamber and various other operations necessaryto provide proper operation of the reaction system 200. The operationand control mechanism 210 can include control software and electricallyor pneumatically controlled valves to control flow of precursors,reactants and purge gasses into and out of the reaction chamber 202. Thecontrol system can include modules such as a software or hardwarecomponent, e.g., a FPGA or ASIC, which performs certain tasks. A modulecan advantageously be configured to reside on the addressable storagemedium of the control system and be configured to execute one or moreprocesses.

Those of skill in the relevant arts appreciate that other configurationsof the present reaction system are possible, including different numberand kind of precursor reactant sources and purge gas sources. Further,such persons will also appreciate that there are many arrangements ofvalves, conduits, precursor sources, purge gas sources that may be usedto accomplish the goal of selectively feeding gasses into reactionchamber 202. Further, as a schematic representation of a reactionsystem, many components have been omitted for simplicity ofillustration, and such components may include, for example, variousvalves, manifolds, purifiers, heaters, containers, vents, and/orbypasses.

The example embodiments of the disclosure described above do not limitthe scope of the invention, since these embodiments are merely examplesof the embodiments of the invention, which is defined by the appendedclaims and their legal equivalents. Any equivalent embodiments areintended to be within the scope of this invention. Indeed, variousmodifications of the disclosure, in addition to those shown anddescribed herein, such as alternative useful combination of the elementsdescribed, may become apparent to those skilled in the art from thedescription. Such modifications and embodiments are also intended tofall within the scope of the appended claims.

What is claimed is:
 1. A method for forming a semiconductor devicestructure, the method comprising: forming a molybdenum nitride film on asubstrate by atomic layer deposition, wherein forming the molybdenumnitride film comprises: contacting the substrate with a first vaporphase reactant comprising a molybdenum precursor; after contacting thesubstrate with the first vapor phase reactant, contacting the substratewith a second vapor phase reactant comprising a nitrogen precursor; andat the same time as or after contacting the substrate with the secondvapor phase reactant, contacting the substrate with a third vapor phasereactant comprising a reducing precursor.
 2. The method of claim 1,wherein the nitrogen precursor is selected from the group comprisingammonia (NH₃), hydrazine (N₂H₄), triazane (N₃H₅), tertbutylhydrazine(C₄H₉N₂H₃), methylhydrazine (CH₃NHNH₂), and dimethylhydrazine((CH₃)₂N₂H₂).
 3. The method of claim 1, wherein the reducing precursoris selected from the group consisting of hydrogen gas (H₂), silane(SiH₄), disilane (Si₂H₆), trisilane (Si₃H₈), tetrasilane (Si₄H₈), andacetylene (C₂H₂).
 4. The method of claim 1, wherein the nitrogenprecursor is selected from the group comprising hydrazine (N₂H₄),triazane (N₃H₅), tertbutylhydrazine (C₄H₉N₂H₃), methylhydrazine(CH₃NHNH₂), and dimethylhydrazine ((CH₃)₂N₂H₂.
 5. The method of claim 1,wherein the molybdenum precursor comprises a binary molybdenum halideprecursor.
 6. The method of claim 1, wherein the molybdenum precursorcomprises a molybdenum chloride.
 7. The method of claim 1, wherein themolybdenum precursor comprises at least one of molybdenum trichloride(MoCl₃), molybdenum tetrachloride (MoCl₄), molybdenum pentachloride(MoCl₅), and molybdenum hexachloride (MoCl₆).
 8. The method of claim 1,wherein the molybdenum precursor comprises a molybdenum fluoride.
 9. Themethod of claim 1, wherein the molybdenum precursor comprises molybdenumhexacarbonyl (Mo(CO)₆).
 10. The method of claim 1, wherein themolybdenum precursor comprises at least one halide ligand.
 11. Themethod of claim 10, wherein the halide ligand comprises chloride orfluoride.
 12. The method of claim 1, wherein the molybdenum precursorcomprises at least one metal-organic ligand.
 13. The method of claim 1,wherein the molybdenum precursor comprises least one organometallicligand.
 14. The method of claim 1, wherein the molybdenum precursorcomprises a cyclic ligand.
 15. The method of claim 1, wherein themolybdenum precursor is selected from the group consisting of molybdenumtrichloride (MoCl₃), molybdenum tetrachloride (MoCl₄), molybdenumhexachloride (MoCl₆) and molybdenum hexafluoride (MoF₆).
 16. The methodof claim 1, wherein contacting the substrate with the third vapor phasereactant is performed after contacting the substrate with the secondvapor phase reactant.
 17. A reaction system configured for forming themolybdenum nitride film of claim
 1. 18. A semiconductor device structurecomprising: a PMOS transistor gate structure, comprising: a molybdenumnitride film formed according to the method of claim 1; a semiconductorbody; and a gate dielectric disposed between the molybdenum nitride filmand the semiconductor body.
 19. The semiconductor device structure ofclaim 18, wherein the molybdenum nitride film comprises between 30atomic % and 60 atomic % molybdenum.
 20. The semiconductor devicestructure of claim 18, wherein the molybdenum nitride film comprisesbetween 40 atomic % and 50 atomic % molybdenum.